1. Field of the Invention
The field of the present invention relates generally to circulating pumps for use in home or industrial water supply systems and, more particularly, to circulating pumps of the type having a housing and manifold attached to a pump motor for installation in a piping system. Even more particular, the present invention relates to such circulating pumps having a housing made from composite or other moldable, non-metallic materials.
2. Background
Circulating pumps are frequently used in piping systems requiring circulation of water. One common example of such use is in the re-circulation of hot water in a hot water supply system used to distribute hot water throughout a house and to a heat exchanger that provides central heating for the house. The circulating pump is usually soldered or brazed into the plumbing system to circulate the water under pressure. The typical circulating pump has an inlet that supplies water to the pump through a manifold, a pump housing or volute having a spiral, round or other shaped impeller chamber, an impeller located in the chamber and a power head (such as an electric motor having a motor housing, stator, bearings, shaft, etc.) to drive the impeller. This type of circulating pump is connected in-line to the standard piping system.
Typically, the various components of a circulating pump are manufactured from metallic materials, such as copper, brass or bronze. In order to obtain the desired shape and finish for these pumps, the pump housing is cast from the metallic material and machined to final shape, making it expensive to manufacture. If the pump is made of an alloy that does not contain lead, as frequently desired by circulating pump users, the materials are generally more expensive, more difficult to machine, more difficult to braze into the plumbing system and more difficult to cast without porosity, therefore making the pump even more expensive to manufacture. An advantage of the metallic cast circulating pump is that users of the pump are familiar with a cast metal pump and can quickly and easily braze the pump into the plumbing system, which is typically comprised of metal piping made of copper or brass.
A circulating pump made of non-metallic material, such as plastic or various composite materials (such as glass and/or mineral reinforced plastic), could avoid many of the problems described above with a cast metal pump. A major disadvantage of a non-metallic circulating pump is that most users are not familiar with connecting a non-metallic pump to a metal plumbing system (i.e., copper tubing) and/or lack confidence in its ability to perform under operating conditions. Because of the lack of experience or confidence, users avoid non-metallic pumps. Concerns regarding dripping leaks and catastrophic failures, which are typically the major liability concern for pump makers or those who install circulating pumps in their systems or equipment, only reinforce the decision to avoid non-metallic pumps.
The typical pump housing comprises a manifold having inlet and pressure side ports, which are cast with the pump housing as a single piece. The pump inlet and pressure side ports are brazed to the metallic piping of the plumbing system. The pump unit, including the pump motor, is supported by the metallic piping. Because the metal manifold and pump unit are brazed to the piping, the unit will not move relative to the piping. If, however, the unit comprises a pump housing with a tubular shaped manifold that is not brazed to the piping system (i.e., one utilizing a joint of telescoping tubular members sealed but not bonded), then the moment force from the overhung weight of the motor about the piping centerline can cause the pump unit to slip and move in a rotary motion about the piping (when the piping is in a horizontal position). This tendency to slip has been a further drawback to the use of a non-metallic pump housing.
To prevent undesirable thermal siphoning of heating system hot water through the pump, a check valve is provided downstream of the pressure side of the pump in the typical circulating pump piping system. The use of the check valve adds additional connections in the plumbing system, which requires more time and results in greater installation cost. For the check valve to be field replaceable, a removable gasketed opening must also be provided. In addition to the cost, the use of the check valve provides multiple additional locations for potential connection failures or leaks.